Re: [Leica] "SureGuard" Photo Lacquer with UV inhibitor

[George Huczek <ghuczek@sk.sympatico.ca>]

At 08:40 PM 09/10/98 EDT, you wrote:
> I have just examined by Epson color prints (3 types of paper)
> that were sprayed with McDonald PRO-TECTA-COTE & then
> left on our patio for 30 days. There is no apparent fading or
> other deterioration compared to the unsprayed one that were
> stored in an album.  
You need to do your test so that you are just considering only one effect
at a time, like the effect of spraying, or just the effect of UV light, but
not both at once.  A better test would be to place two prints on the patio
side-by-side -- one sprayed and the other unsprayed.  A second set of
prints can be stored in darkness under similar conditions -- one sprayed
and the other unsprayed.

> Question - doesn't window glass or any modern type glass also
> absorb UV light?  If so, then why do my unsprayed prints that
> are kept near a closed glass picture window start to fade in 30
> days. Are there other factors besides UV light that are involved?

There are several things involved.  UV light can affect the print, and so
can atmospheric pollution.  Keeping the print in a hermetically sealed
frame isn't a good idea either.  It keeps out things like low level ozone
and SO2, but it keeps in chemicals which are produced naturally during
print deterioration.  Some of these trapped residuals act as catalysts,
accelerating the deterioration process.  Framed prints must be allowed to
"breathe", contrary to what one would expect intuitively, since it also
allows the environmental pollutants access to the print.
   Ctein, in "Post Exposure" (1997) shows an RA-4 print made in 1981 of an
early shuttle mission.  Sprayed copies of the print have discoloured badly.
 Unsprayed copies are in good condition.  The materials are not the same as
those you mentioned, but I would take Ctein's test results as general a
caution against spraying.  His methods and results are reliable.
   In a recent Photo Techniques article, which is an excerpt from the book,
he shows what happens to B&W RC papers (Agfa multigrade in his tests).  His
test print has four regions: one is unprotected, a second has selenium
toning, a third has Agfa Sistan treatment, and a fourth has both Sistan and
selenium treatment.  The print was then sealed with a vapor barrier and
stored in a dark place for several months, to eliminate the effects of UV.
The untreated area shows typical signs of deterioration, with loss of Dmax
in the darkest regions.  Exhibition Agfa RC prints which he and a colleague
have sold are showing noticeable silvering out.  Those prints are framed.
Apparently Agfa has now addressed this problem, adding inhibitors to the
paper to tame the culprit -- the titanium oxide brightener.
   Your patio tests are not conclusive.  You have to leave the prints in
their test environments longer, and your tests have to be set up
empirically with proper controls.  Your paper used for printing may also be
a factor, since most computer paper is not acid free or free of alkaline
buffers.  One of the problems in testing for archival permanence is that
you can not accelerate the tests -- say by blasting the print with 100
times as much UV light as it would normally encounter.  You can not
extrapolate that 1 day of high intensity exposure would equal 100 days of
normal exposure.  Some of the rate determining steps in the chemical
reactions taking place can not be sped up this way.  The issue of archival
print permanence is a complex one, often containing considerable debate.


 _
[o] -GH